.nav-bar {
  display: flex;
  line-height: 44px;
}
.left, .right {
  height: 44px;
  width: 70px;
  background-color: red;
}
.center {
  flex: 1;
  height: 44px;
  background-color: blue;
}
.nav-item {
  text-align: center;
}